The present invention relates to a movable driven feeding apparatus for high shelf stores and, more particularly, to a feeding apparatus supported on rollers and having drive elements which are independent of the weight of the feeding apparatus and are effective in two or more planes disposed one above the other.
Movable feeding mechanisms for high shelf stores of one type have in the past been driven at one of their ends by the same rollers that support the weight of the feeding apparatus on the track. In this structure, only if the roller bearings are uniformly lubricated can the weight remain constant. Therefore, the rolling resistance of the entire feeding apparatus remains substantially the same from start to stop, while the friction value which effects a uniform drive and determines the slip between roller and rail depends on external influences (e.g., dust) and, therefore, varies. Furthermore, when such a feeding apparatus is accelerated at one end only, the non-driven portions of the feeding apparatus lag somewhat with respect to the driven end and cause the entire feeding apparatus to start vibrating in the direction of travel. As a result such vibrations must be allowed to subside before a feeding from and to the feeding device is possible.
The same result occurs also when such an apparatus is decelerated too strongly by braking or when the drive is nonuniform and jerky. Only when acceleration and speed of the feeding apparatus are very low can the vibrations and consequent waiting periods be avoided. In this case, however, a longer traveling period will occur instead of the long waiting periods. In order to shorten traveling time or waiting periods, such feeding devices have been reinforced but at high cost. Thus, to be sure, starting and braking vibrations were reduced, but the high weight of the feeding apparatus and reinforcement prevented a speedy start and stop.
Another type of very high movable feeding apparatus for high-shelf stores is driven in several superposed planes with as much synchronization as possible in order to ensure uniform acceleration at all levels and to move the stored items exactly as required. In such an apparatus it is conventional to provide gears as the drive elements in the drive levels or planes. Stationary or static racks mesh with the gear drive elements which are synchronized by common shafts. Such a positive transmission seeks to ensure that a fixed drive system revolution rate is converted into a fixed distance traversed by the feeding apparatus. However, many difficulties arise when the feeding apparatus is of great height and, in particular, when it is a hanging construction since there is a significant lack of rigidity. Thus, the constantly changing transmission area defined by the gears and their associated static racks cause oscillations to arise in the drive shafts. Input torques experience phase displacement due to the length of the shafts. Furthermore, the necessary backlash which, however, is increased even further because of wear gives rise to impermissibly high tolerances when moving the individual stored items. In such a system, an error in the drive mechanism can cause a drive element to advance or retard without any ability to correct the error. When the tolerances become too great it is therefore necessary to carry out extensive replacement of the gears and racks.
One solution to correct this problem has been suggested in German Offenlegungsschrift No. 1,531,888 whereby an error in movement is to be corrected by switching a friction gear drive to a rack and pinion drive in the second plane. However, this drive is not suitable for balancing out errors and play in the rack and pinion pairs. Although the use of rack and pinion drive pairs enables the torque of the individual drive units to be exactly assigned to each other, the tooth backlash necessarily limits the accuracy of movement of the stored items. Again, when such drive pairs become worn, very expensive repair work is required. Thus it can be readily seen that in previously known drive mechanisms it was not possible to effectively eliminate the wear occuring as a result of repeated operation of the feeding apparatus over a period of time. The contact between the working surfaces leads not only to wear but also to considerable noise. Furthermore, wear is also increased by the exposure of the meshing working surfaces to a particularly high degree of dirt.
The object of this invention is to construct a movable, very high feeding apparatus in such a manner that strong positive and negative accelerations and high traveling speeds are possible, while vibration of the entire feeding apparatus in the traveling direction is prevented.
A further object of the present invention is the provision of a feeding apparatus for finding a high-shelf store driven in various superposed places and insensitive to a large degree to wear and dirt without, however, sacrificing any accuracy in placing or extracting an item.
A still further object of the present invention is the provision of an improved feeding apparatus for accurately finding a desired item at any level independently of wear and so that only inexpensive repairs are needed when extensive wear has occurred.
The foregoing objects have been achieved in accordance with the present invention by providing a feeding apparatus with positive drive elements independent of the weight of the feeding apparatus operated in two or more superposed planes and connected with working surfaces stretching along the length of the track of the feeding apparatus.
A feeding apparatus according to the present invention with positive drive elements operated in two or more superposed planes can be rapidly sped up or slowed down by the uniform action of acceleration forces without undergoing vibration. To assure such operation, the drive elements must be operated at the same acceleration or number of revolutions in order to produce a uniform drive speed in all driven planes of the feeding apparatus. According to the present invention, each drive element is connected with a regulating mechanism which measures the distance travelled by each drive element by means of primary elements and then balances each such measured distance in relation to a nominal or rated value common to all regulating mechanisms by controlling the drive of each drive element. If, for example, the feeding apparatus is driven by drive rollers with a vertical shaft meshed in frictional engagement with horizontal rails constituting the running or working areas, the regulating mechanisms assure that all the drive elements have the same speed or have the same acceleration. Thus the present invention has made the harm ordinarily caused by wear and dirt in a positive drive system only of secondary importance by providing a drive system whose positive meshing and regulating means enable each of the drive elements to be moved to an exactly predetermined item quite independently of wear or dirt on the working surface.
The regulating mechanism assigned to each drive element for directly registering the distance travelled by the associated drive element determines by means of the pick-up value the accuracy with which the feeding apparatus moves to an item controlled at every drive level with respect to a common rated value. It is not only the relative movements of the individual drive levels that are regulated during braking or accelerating but also those arising from high unilateral stress on the feeding apparatus due to strong acceleration or braking of the loaded carriage, thereby enabling the feeding apparatus to have a particularly light design which is more inexpensive to construct. Moreover, time and money can be saved by virtue of the high acceleration values obtainable due to the low weight made possible by the economically designed regulating drives. Because of the upright design, the feeding apparatus needs to be buckle-resistant only over the distance between two drive elements. Where a suspended design is employed the permissible horizontal deflection must not be exceeded between two drive elements, thus the overall height can be disregarded. The distance is registered directly by means of a primary element, and not by means of secondary values such as friction gear revolutions, thereby eliminating disturbance variables.
The rail surfaces which bear the weight of the rollers and thus the weight of the entire feeding apparatus, must be substantially horizontal. Impurities, such as oil drops, dust, etc., adhere, therefore, to the surface. However, a shock-free, positive drive requires a stable condition of the friction gears. Such a stable condition of the friction gears, however, can only be assured for a longer period of time if, by the arrangement of these friction gears, deposits are prevented on one or both parts of the gear which might disturb the uniform traveling operation of the feeding apparatus. It is, therefore, advisable, to position, in one embodiment of the present invention, the surface of the friction gear vertically so as to prevent soiling. The pressure forces necessary for a safe functioning of the friction gear can be produced by simple, structural devices, e.g., pressure springs.
The axle of the drive rollers runs vertically and the running surface is also vertical. Not only does this arrangement guarantee that the drive is independent of the net weight of the feeding apparatus in order to achieve continuity of operation and wear conditions but it also prevents oil, dirt or the like from settling on the working surface. As will be readily appreciated the presence of such foreign matter on the working surface can lead to uneven force transmission and a high degree of wear which, particularly when the force transmission is uneven, would require the regulating drive to have a high power requirement in order to balance out the unevenness.
On advantage of the arrangement constituting the present invention is that the friction gear drive is able to be moved accurately to any point without the wear of the permissible wear area leading to any tolerances. Moreover the friction gear drive always has the same force transmission area so that the drive does not induce oscillations in the feeding apparatus as can arise due to the periodic yielding behavior of some of the apparatus components. In addition, the replacement or repair of the friction surfaces can be accomplished more economically.
According to another feature of the present invention the distance covered by a drive element is the rated value for the regulating means connected with other drive element. Thus, the leading drive element can be controlled by conventional regulating control equipment, safety switches, and even manually such that the secondary regulating circuits ensure that the feeding apparatus accurately follows the leading drive in all drive levels.
Another embodiment of the present invention employs linear motors as drive elements which are in magnetic force mesh with work areas which, in particular, can be made of aluminum. Such arrangement enables the entire feeding apparatus to be driven contact-free so that the condition of the surface, dirt on the work surface or the like is of no importance. Furthermore, the drive is virtually silent and is without moving parts in the drive elements. Thus, the drive elements are completely wear- and maintenance-free. However, the linear motors and the working surface can be given an additional friction layer on their opposed surfaces so as to allow reciprocal movement when impermissible vibrations occur without causing any damage.
A still further embodiment of the present invention uses electrical guide magnets connected with one regulating device to keep the lateral distance constant between the feeding apparatus and the shelf made of ferromagnetic material opposite a working track on the shelf side. This arrangement eliminates any need whatsoever for distance rolls or guide rolls whereby, due to the inertia of the regulator controlling the guide magnet, a damping action is achieved and effectively counteracts the vibrations of the feeding apparatus. A guide magnet can also be associated with the linear motor means to ensure that the air gap between a linear motor and the corresponding working surface is always the optimum amount and to assist in completely eliminating mechanical friction which causes power losses, wear and noise.